answer: k = 6, x ∈ {-2, 8}
explanation:
to solve for k: plug -2 in for x and solve.
(-2)^2 - k(-2) - 16 = 0
4 + 2k - 16 = 0
-12 + 2k = 0
2k = 12
k = 6
to find any missing solutions: plug k back in
x^2 - 6x - 16 = 0
factor:
(x - 8)(x + 2) = 0
x ∈ {-2, 8}
